1. Field of the Invention
The present invention relates to a heating cooker, and particularly to a technique of automatically baking cakes, etc., with the heating cooker.
2. Description of the Prior Art
A heating cooker such as an electronic oven generally has a grilling function and an oven function. The grilling function is achieved with a flat heater attached to the ceiling of the cooker to cook fish, meat, etc., with radiant heat, while the oven function is achieved with a sirocco fan and a sheathed heater arranged on the back of a heating chamber of the cooker to bake bread, cakes, etc., with hot air circulated in the cooking chamber.
To automatically control the grilling and oven functions, a conventional technique employs a weight sensor. With the weight sensor, the technique measures a total of the weight of food to be cooked and the weight of container of the food, calculates a heating time according to the total weight, and after the elapse of the heating time, automatically stops heating the food. Another conventional technique employs a weight sensor to calculate a base time and a temperature sensor to detect vapor evaporating from heated food and to calculate an additional heating time, from which the technique determines a total heating time.
Food, particularly bread or a cake must be baked under careful control to form air bubble inside it. In automatically baking the bread or the cake, the above conventional techniques raise the following problems:
1) If no preheating is done or if the cooking chamber is not sufficiently cooled, the conventional techniques cannot correctly calculate a heating time of the bread or the cake. After repetitive use of the oven, bread or cakes may be overbaked. Under the increasing need of cooking with no preheating, this problem is serious.
2) The conventional techniques restrict the weight of a container of food to be cooked. Cake molds may be made of stainless steel, heat-resistant glass, aluminum, paper, etc., which have different weight. The weight sensor of the conventional techniques restricts the material of the container. If it is unrestricted, the conventional control techniques may be useless because the weight sensor measures a total of the weight of a mold and the weight of food contained in the mold. Namely, the baking of bread or a cake is greatly influenced by the weight of a mold to be used for baking the bread or the cake. If the mold is light weight, a baking time may become shorter to make the bread or the cake half-baked.
3) The weight sensor must be connected with a top plate of the cooker. This arrangement limits the size of the top plate so that a space in the cooking chamber may not effectively be used. Compared with a usual square top plate, the top plate of the above techniques must have limited size and shape which may reduce the quantity of food to be cooked on the top plate. It is possible to employ a special top plate, but it may increase the number of accessories and the cost and deteriorate handling convenience of the cooker.
4) The control means employed by the above techniques includes only the weight sensor. This limits a base time for each menu. This means that a menu which is selected with one selection key of the cooker does not have flexibility in cooking times. For example, there are various kinds of cakes such as sponge cakes, pound cakes, madeleines, and roll cakes. The automatic control of the conventional techniques, however, cannot deal with a variety of these cakes because they involve different heating times.
Thus, the conventional automatic cooking techniques for the heating cooker, such as the electronic oven employing the weight sensor, have the problems of setting an improper heating time for repetitive use, limiting the size of the top plate of the cooker to spoil effective use of space in the cooking chamber, being influenced by the weight of a container for the food to be cooked, and limiting the flexibility of cooking time for each menu.